IMPORTANCE OF BEACH, MUDFLAT AND MARSH HABITATS TO MIGRANT SHOREBIRDSON DELAWARE BAY

Shorebirds migrate over long distances from breeding to wintering grou nds, stopping at a few bays and estuaries to refuel. Most information on migration of shorebirds concentrates on population dynamics and for aging behavior on intertidal habitats, We studied the behavior of shor ebirds on mudflats, beaches and marshes on Delaware Bay to understand how they use different habitats. Dense flocks of shorebirds concentrat ed on a tidal mudflat, but shorebirds used all the habitats, including several marshes. The over all percent of shorebirds feeding ranged fr om 34% (open beach), and 59-63% (tidal and nontidal marshes), to 80% ( tidal mudflat). Variations in the percentage of shorebirds engaged in feeding, resting and other behaviors depended on location, date, time, tide and species. A higher percentage of shorebirds fed during the mi ddle of migration, in early to mid-morning, and during low and rising tides than at other times. Some shorebirds fed on the marshes and mudf lats during all tidal states, but none fed on beaches at high tide (be aches were too narrow). Within each habitat, the highest percentage of shorebirds engaged in foraging during low tide (marshes) or rising ti des (mudflats and beaches). Using the percentage of shorebirds engaged in foraging as an indication of foraging value for each habitat type within the landscape, we concluded that a mosaic of habitat types rang ing from mudflats to high marshes is essential to sustain the high pop ulations of shorebirds that use Delaware Bay during spring migration. Copyright (C) 1996 Published by Elsevier Science Limited